physics

Hibakusha

Hibakusha is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hibakusha rather than just read about it. In short: Hibakusha (pronounced [çibaꜜkɯ̥ɕa] or [çibakɯ̥ꜜɕa]; Japanese: 被爆者 or 被曝者; lit. 'bombing survivor' or 'person affected by exposure [to radioactivity]') is a word of Japanese origin generally designating the people affected by the atomic bombings of Hiroshima and Nagasaki by the United States at the end of World War II. Definition The word hibakusha is Japanese, originally written in kanji.

Key takeaways

Hibakusha belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hibakusha to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hibakusha from memory before moving on to harder problems.

Reference excerpt

Hibakusha (pronounced [çibaꜜkɯ̥ɕa] or [çibakɯ̥ꜜɕa]; Japanese: 被爆者 or 被曝者; lit. 'bombing survivor' or 'person affected by exposure [to radioactivity]') is a word of Japanese origin generally designating the people affected by the atomic bombings of Hiroshima and Nagasaki by the United States at the end of World War II.

Definition The word hibakusha is Japanese, originally written in kanji. While the term hibakusha 被爆者 (hi 被 'particle indicating passive mood of the subsequent verb' + baku 爆 'to bomb' + sha 者 'person') has been used before in Japanese to designate any victim of bombs, its worldwide democratization led to a definition concerning the survivors of the atomic bombs dropped in Japan by the United States Army Air Forces on 6 and 9 August 1945. Anti-nuclear movements and associations, among others of hibakusha, spread the term to designate any direct victim of nuclear disaster, including the ones of the nuclear plant in Fukushima. They, therefore, prefer the writing 被曝者 (replacing baku 爆 'to bomb' with the homophonous 曝 ' to expose to s.t.') or 'person exposed to radiation, a person affected by nuclear exposure'. This definition tends to be adopted since 2011. The legal status of hibakusha is allocated to certain people, mainly by the Japanese government.

Official recognition The Atomic Bomb Survivors Relief Law defines hibakusha as people who fall into one or more of the following categories: within a few kilometers of the hypocenters of the bombs; within 2 km (1.2 mi) of the hypocenters within two weeks of the bombings; exposed to radiation from fallout; or not yet born but carried by pregnant women in any of the three previously mentioned categories. The Japanese government has recognized about 650,000 people as hibakusha. As of 31 March 2026, 91,105 were still alive, mostly in Japan. The government of Japan recognizes about 1% of these as having illnesses caused by radiation. Hibakusha are entitled to government support. They receive a certain amount of allowance per month, and the ones certified as suffering from bomb-related diseases receive a special medical allowance. The memorials in Hiroshima and Nagasaki contain lists of the names of the hibakusha who are known to have died since the bombings. Updated annually on the anniversaries of the bombings, as of August 2026, the memorials record the names of more than 550,000 hibakusha; 353,639 in Hiroshima and 204,708 in Nagasaki.

In 1957, the Japanese Parliament passed a law providing free medical care for hibakusha. During the 1970s, non-Japanese hibakusha who suffered from those atomic attacks began to demand the right to free medical care and the right to stay in Japan for that purpose. In 1978, the Japanese Supreme Court ruled that such persons were entitled to free medical care while staying in Japan.

Korean survivors During the war, Korea had been under Japanese imperial rule and many Koreans were living in Hiroshima and Nagasaki at the time of the atomic bombings. More than 2 million Koreans migrated to Japan during the colonial period as a result of financial hardship on the peninsula. Others were either mobilized as laborers or soldiers during World War II. Those who remained in postwar Japan after the atomic bombings were called Zainichi Korean hibakusha. According to recent estimates, about 20,000 Koreans were killed in Hiroshima and about 2,000 died in Nagasaki. It is estimated that one in seven of the Hiroshima victims was of Korean ancestry. The exact number of Korean victims remains unknown; however, the amount of those exposed to radiation increased as laborers were mobilized to provide response and relief to areas that were directly affected. For many years, Koreans had a difficult time fighting for recognition as atomic bomb victims and were denied health benefits. Some reported discriminatory treatment in applying for allowances and survivor certificates. Others were unable to access information on government relief and healthcare due to literacy barriers. Some of these issues have been addressed in recent years through lawsuits. Efforts to commemorate Korean victims have been contentious within the context of both North-South Korean divisions, as well as Korean-Japanese relations. The emergence of Cold War geopolitical tensions complicated Zainichi Korean hibakusha efforts to advocate for redress and recognition for Korean victims as the Zainichi community grappled with divisions on their home peninsula. Several Zainichi Korean hibakusha memorials exist in Japan today, including the Chosen-jin Hibakusha Memorial in Nagasaki Peace Park, as well as the Hiroshima Kankoku-jin Hibakusha Cenotaph. The cenotaph was heavily disputed in terms of its original placement outside of the Peace Memorial Park, as well as its engravings. At the end of the 1990s, joint talks between Hiroshima City mayor Hiraoka Takashi, as well as members of both Mindan and Soren—the two, prominent Zainichi Korean organizations in Japan—helped facilitate the transfer of the cenotaph within the park, which was completed in 1999.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Hibakusha

Start with the simplest possible case. Write down what Hibakusha claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hibakusha before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hibakusha ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hibakusha

In research: Hibakusha appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hibakusha in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hibakusha is common in secondary-school and first-year university syllabi. It links to neighbouring topics Anti–nuclear weapons movement, Hibakusha, Nuclear warfare, so understanding it makes those chapters shorter.
In everyday life: Look for Hibakusha outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Hibakusha in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hibakusha means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hibakusha out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hibakusha in simple terms?

Why does Hibakusha matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hibakusha?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hibakusha.